TRIPOLI — U.S. air strikes are easing the passage of Libyan forces as they seek to clear ISIS from the militant group’s former North African stronghold of Sirte, a senior field commander said on Wednesday.

Mohamed Darat said the first strikes, which took place on Monday, had helped Libyan brigades under his command secure the Dollar residential neighborhood by targeting militants who had been holding out on the district’s edge.

Libya’s U.N.-backed government requested the strikes nearly three months into a campaign that had slowed due to heavy casualties from sniper fire, mines and mortars.

“In the last two houses in this area we faced strong resistance, so we asked (the U.S.) to hit that site,” said Darat, speaking from a part of Dollar captured last week. “We moved back and they struck.”

A U.S. defense official said there were five strikes on Monday and two on Tuesday. The Pentagon said the first targets included two tanks, construction and military vehicles and a rocket launcher.

Losing Sirte would be a huge blow for ISIS, which took control of the city midway along Libya’s Mediterranean coastline last year. The group is already under pressure from U.S.-backed campaigns in Syria and Iraq.